Boeing has launched an investigation into a new quality problem with its 787 Dreamliner aircraft. The company discovered that hundreds of fasteners on the fuselages of some undelivered jets have been incorrectly installed, according to two anonymous sources familiar with the matter.

The issue revolves around the incorrect "torquing" or tightening of more than 900 fasteners per plane at a Boeing facility. These fasteners are split equally between both sides of the jet's mid-body. While there is currently no immediate concern about flight safety, Boeing is working to determine the cause of the problem. Once the investigation is complete, the company will decide if any rework needs to be done, as reported by the sources.

Boeing has confirmed the ongoing checks, stating that it doesn't anticipate a significant impact on deliveries. A spokesperson for the company assured that the in-service fleet can continue to operate safely. They added that Boeing is taking the necessary time to ensure all airplanes meet their delivery standards. The company is also working closely with its customers and the Federal Aviation Administration (FAA), keeping them updated on the progress.

FAA Administrator Mike Whitaker acknowledged the issue but refrained from providing further comment. He announced that he would be visiting Boeing's 787 plant in South Carolina on Friday to gather more information about the situation from the facility's personnel.

Following this news, shares of Boeing initially dropped 1.7% but later recovered to remain flat. The American planemaker has faced increased scrutiny from regulators and customers since a January 5 incident involving a smaller 737 MAX aircraft operated by Alaska Airlines, which had to make an emergency landing due to a blown-out fuselage panel mid-flight.

The latest manufacturing flaw was discovered at Boeing's South Carolina plant, where the 787's lightweight carbon-composite skin is attached to skeletal supports called longerons inside the fuselage sections. Sources revealed that the affected fasteners were torqued from the wrong side, using the head instead of the associated nut. In response to previous incidents, Boeing had already issued a bulletin to suppliers in January, outlining procedures to ensure proper torqueing of bolts following inspections of grounded 737 MAX 9s.

Despite the ongoing investigation and production slowdowns unrelated to the current issue, tracking data confirms that 787 deliveries are still taking place, albeit at a slower-than-usual rate. FlightRadar24 reported that one 787-10 model departed for its European customer on Wednesday. Airlines, however, remain concerned about existing delivery delays, with some buyers estimating average delays of several months.